Finger-Lickin' Evil

Evil girls (generally cat girls or dark magical girls) are frequently armed with razor-sharp fingernails or claws as their primary melee weapon. If such is the case, her trademark gesture is to lick her claws in a cat-like fashion with a sinister grin on her face, sometimes while blood drips from them.

Masato of Mermaid Saga is one of the few male examples of this trope. While he doesn't have sharp finger-based implements of doom, he does make a point of licking the blood off his fingers after gouging Yuta's eye out to show how damn evil he is.

Variation: Ren licks his chops in Shaman King while his face has blood on it.

Another Variation: Road Kamelot from D.Gray-man licks the blood off of the sharpened candle she pierced Allen with.

Rob Lucci, another male example, licks the blood off his thumb once during his fight with Luffy in One Piece. It's unclear whether the blood is his or Luffy's. (He does have cat claws, but they weren't at the time.)

In the OVA of Jojo's Bizarre Adventure, Dio rips through a group of civilians with a single slash of his hand, then laughs to Jotaro as he licks the blood from it.

Licking his fingers is also one of the multiple unpleasant habits of the villain Magenta Magenta from the seventh series of the manga.

In a battle between Ranma and Ryoga from Ranma ½ manga, Ryoga manages to cause a small cut on Ranma's face. Ranma proceeds to wipe the blood off with his hand and lick it while saying something to the effect of looks like I'm going to have to get serious.

Lady Deathstrike has extendible adamantium fingernails (originally she was just an insane swordswoman from Daredevil, now better known as a foe of the X-Men, and Wolverine in particular) and occasionally licks them.

In Wizard's First Rule, Big Bad Darken Rahl has a few tics, among them licking his fingertips and running them over his lips and eyebrows, stemming from his being burned by Wizard's Fire when he was a boy.

In both the Metal Gear Solid game and comic, Sniper Wolf gashes Snake's face with her nails to symbolise that he's her "special prey". In the comic, she licks her fingers. It looks cool as hell until the plot explains to you that the reason the Quirky Miniboss Squad is so worried about Snake is that he's carrying a deadly virus in his bloodstream. Though considering she's a Death Seeker it makes sense.

WWE wrestler Mickie James lacks the razor-sharp claws, but still managed to pull off this trope off by busting Trish Stratus' forehead open, then wiping her hand against it and licking the blood off her fingers.